Neuron or axon degeneration plays a central role in the proper development of the nervous system and is a hallmark of many neurodegenerative diseases including, for example, amyotrophic lateral sclerosis (ALS), Alzheimer's disease, and Parkinson's disease, as well as traumatic injury to the brain and spinal cord. These diseases and injuries are devastating to patients and caregivers, and also result in great financial burdens, with annual costs currently exceeding several hundred billion dollars in the United States alone. Most current treatments for these diseases and conditions are inadequate. Adding to the urgency of the problems created by these diseases is the fact that many such diseases are age-related, and thus their incidence is increasing rapidly as population demographics change. There is a great need for the development of effective approaches to treating neurodegenerative diseases and nervous system injuries.